Calendar recurrences err msg"Cannot open this item. The object ...

After a recent upgrade to outlook 2003 - calendar recurrences now give err msg
"Cannot open this item. The object could not be found.". This occurs on new
additions into the calendar. In my pursuit I added user entry as owner under
calendar properties but err still occurs.
I'm new to supporting all M'soft products & know nothing much about behind
the scenes! So firstly, I'm wondering if there is a knowledge base where I
can input this error (for outlook 2003) to perhaps give me some ideas. I
would also like to know how outlook writes these entries...i know that
there's a .pst file & that's about all i know behind the scenes. Any
information or thoughts would be most appreciated :-)

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Kazza